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Alan Guth, whose inflation Universe scenario may help to explain why our observable universe so close to flat and homogeneous condition
the Cool morning in December, 1979 in Palo Alto Alan Guth that there are hand pedaled bike, hurrying to his office in the theoretical physics group at SLAC, Stanford linear accelerator center having Reached the desktop, he opened the notebook to a new page and wrote:
AMAZING a GUESS: this kind of supercooling can explain why the universe today is so incredibly flat — and therefore, to resolve the paradox of the fine tuning that Bob's dick had described in his lectures at the bottom of Einstein.
He carefully circled these words a rectangular frame. Then another Being a scientist, you live for the day when you will be able to achieve a result — this may be a theoretical conjecture and experimental discovery so amazing that it deserves to be framed. In rare cases, the result is worthy of a double frame — usually it radically changes a person's life, and along the direction of progress of scientific thought. According to himself, Gut, other results would have to circle double border in his notebooks there. And that notebook, which he used during the work at SLAC, is now part of the exposition of the Adler planetarium in Chicago, opened on the page with the above quoted entry.
the Gut on the trail of the script, today known as "inflation." The idea that the early universe was filled with a temporary form of dark energy, ultra high density, what caused space to accelerate at an incredible pace (the aforementioned "hypothermia"). This simple assumption is able to explain almost everything that relates to the conditions observed in our early Universe — from the space geometry to the distribution of density perturbations in the cosmic microwave radiation. Although we do not yet have definitive evidence that inflation actually happened, this idea may have been most influential in cosmology over the past few decades.
this, of course, should not be the truth If in the early Universe during a period of time dominated by dark energy with high density, it is possible to understand why the universe evolved to the state where she obviously was in the early years. However, we are putting ourselves in danger to overlook an important question: why the universe in General was under the power of dark energy? Inflation in itself does not give any answer to the puzzle of why the entropy in the early Universe was low, with the exception of the assumption that when the origin of the Universe entropy was even lower (which may be a slight cheating). Nonetheless inflation is incredibly attractive idea consistent with the observed properties of our early Universe. And thanks to her we came to some surprising conclusions that were not foreseen even the Gut when I first proposed this scenario — including, as we soon learn the way to give a realistic idea Multilines. According to most currently working cosmologists, one or another version of inflationary theory, is likely to be in the correct result. The only question is, why did inflation ever happen?
the Curvature of space.
Imagine that you took a pencil and try to put it on the tip of the stylus. Obviously, it will immediately start to fall. But if your disposal was extremely stable surface, and you would be a true master of balancing, you could set this design so that the pencil remains in a vertical position for a very long time. For example, more than 14 billion years. This is a good example of our Universe, and the pencil is such of its characteristics as curvature of space. In fact, it's not the most complicated concept, but cosmologists are often artificially complicate it, saying something about "the curvature of space—time", about the "curvature of space". These are different things, and we have each time from the context to guess what was meant. As well as space — time may have curvature, the curvature may be in space itself, and the question of how curved the space, completely not related to the question of iskrivlennoi of space — time.
One of the problems that can potentially emerge when discussing the curvature of space itself is that General relativity gives us the ability to cut space — time into three-dimensional copy of evolving in time-space in many different ways; the definition of "space" is not unique. Fortunately, in our observable Universe there is a natural variant of this slicing: we define "time" so that the density of matter remained approximately the same in space on large scales, but decreased with the expansion of the Universe. In other words, the distribution of matter determines the natural resting coordinate system in the Universe. It is in any case does not violate the principles of relativity, as it reflects the properties of one particular configuration of matter, not the underlying laws of physics.
In General, the space is completely arbitrary way to bend at different points, and in order to cope with the mathematics that describes the curvature, was developed a special discipline called differential geometry. But cosmologists lucky space when considering very large distances is uniform and looks the same in all directions. In such a situation, it is sufficient to specify one value — "spatial curvature" to learn about the geometry of three-dimensional space. The curvature of space can be expressed using a positive number, negative number or zero. If the curvature is zero, then we naturally say that space is "flat" and has all the geometric characteristics in the usual sense. These characteristics were first formulated by Euclid and include properties such as "parallel lines never intersect" and "the sum of the angles of a triangle equal exactly 180 degrees". If the curvature is positive, the space is reminiscent of the surface of the sphere, except that it is three-dimensional. A line parallel to any site, will eventually intersect, and the sum of the angles of a triangle exceeds 180 degrees. If the curvature is negative, space is like a saddle or a potato chip. The lines parallel to some part, disagree in part, and the sum of the angles of a triangle — well, you probably guessed it.
the Options of spaces with constant curvature. Top to bottom: positive curvature, as on a sphere; negative curvature, as on a saddle; zero curvature, as on a flat surface.
According to the rules of General relativity, if at birth the universe was flat, it remains flat. If it appeared in a contorted state, the curvature gradually as the expansion of the Universe decreases. However, as we already know, density of matter and radiation is also reduced. (While you even forget that you ever heard about the term dark energy, because it puts everything on the head). Writing equations can be seen that the density of matter or radiation decreases faster than the contribution of the curvature of space. Compared to matter and radiation, the curvature of the expansion of the Universe is having an increasing impact on the evolution of the Universe.
Therefore, if the early Universe was present in at least an appreciable contribution of the curvature, the curvature of the Universe today should be obvious. A flat universe is like the pencil, put the tip of the stylus: the slightest deviation left or right will immediately lead to the fall of the pencil. Similarly, any smallest deviation from the ideal plane in the early years should with age becomes more noticeable. But observations show that the universe looks very flat. As far as can be judged, there is no measurable curvature in the contemporary Universe is not observed.
This state of Affairs is known as the flatness problem. Times the universe is so flat today, it had to be incredibly flat in the past. But why?
the problem of the flatness has a certain similarity with the problem of entropy, which we discussed in the previous Chapter. In both cases, it's not a terrible discrepancy between theory and observation — it is enough to postulate that the early universe was in a certain form, and then the puzzle fits together nicely. The problem is that "some form" creates the impression of unnatural shape and force finely adjusted, and without any obvious reason.
In the end, he decided to return to MIT, where he completed graduate school, and to this day he teaches at the school.
the Excerpt from the book by S. Carroll "Eternity. In the quest for the ultimate theory of time"
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